A known variable valve timing control device which changes opening and closing timings of an intake valve and an exhaust valve in accordance with an operation status of an internal combustion engine (hereinafter also referred to as an engine) is practically employed. The variable valve timing control device includes a mechanism that changes the opening and closing timings of the intake and exhaust valves which are opened and closed in accordance with the rotation of a driven-side rotation member by changing of a relative rotation phase of the driven side rotation phase relative to a driving-side rotation member (hereinafter also referred to as a relative rotation phase) by the operation of the engine.
The variable valve timing control device conventionally changes the relative rotation phase by an oil pressure. However, by the recent employment of an electric automobile, an electric valve opening and closing timing control device changing a relative rotation phase electrically by employment of an electric actuator (motor) is developed. The electric variable valve timing control device changes the relative rotation phase by the motor, and thus the relative rotation phase is speedily changed in accordance with an order from an ECU.
The aforementioned electric variable valve timing control device is disclosed in JP2017-115601A (hereinafter referred to as Patent reference 1). According to Patent reference 1, the variable valve timing control device is provided with the driven-side rotation member (ring gear) including an internal teeth portion which is accommodated inside the driving-side rotation member (outer case) so as to be relatively rotatable therewith. The variable valve timing control device further includes an inner gear which is disposed inside the ring gear, the inner gear including an external teeth portion which meshes with a part of the internal teeth portion of the ring gear. The variable valve timing control device further includes an electric actuator (an electric motor) which drives the inner gear, and a coupling member which connects the driving-side rotation member and the inner gear with each other.
According to Patent reference 1, the driving-side rotation member and the driven-side rotation member are disposed so as to be rotatable about a rotation axis, and the inner gear is disposed so as to be rotatable about an eccentric axis which is in parallel with the rotation axis. Accordingly, a first engagement portion of the coupling member is engaged with the driving-side rotation member, and a second engagement portion of the coupling member is engaged with the inner gear.
According to Patent reference 1, the coupling member includes a pair of first engagement arms extending radially outward, and groove portions engaged with the first engagement arms are formed at an outer circumferential portion of the driving-side rotation member. The coupling member further includes a pair of second engagement arms in a direction orthogonal to an extending direction of the first engagement arms, and protrusions being fitted to engagement recessed portions of the second engagement arms are formed at the inner gear.
According to Patent reference 1, the first engagement arms and the grooves are in contact with one another, and the protrusions are in contact with the engagement recessed portions of the second engagement arms, and thus, in a case where alternating torque is applied to a camshaft, contact noises are generated by a phenomenon in which the contact and the separation at the contact portions repeatedly occur. Accordingly, undesired sound may be generated.
A need thus exists for a variable valve timing control device which is not susceptible to the drawback mentioned above.